He was hired by BuzzFeed in December 2011. He has appeared on MSNBC, Fox News, CNN, NPR, PBS, and C-SPAN. On October 3, 2016, Kaczynski announced he was leaving BuzzFeed and joining CNN.
At 19, Kaczynski had a bout of pancreatitis leading him to eschew smoking and alcohol.
He has worked as an intern for the Republican National Committee and was an intern in 2011 in the office of Congressman Bob Turner.
Kaczynski attended college at Ohio University, but got involved with political reporting and then transferred to St. Johns University to study early American history. He enrolled in online courses to meet his degree requirement but did not eventually graduate.
Kaczynski got his start by emailing reporters' tip boxes with clips he found of politicians contradicting themselves.
In March 2012, Kaczynski uncovered numerous clips of Mitt Romney supporting an individual mandate, contradicting his then-current campaign position. He also uncovered a clip of Barack Obama protesting at Harvard while at law school over a lack of faculty diversity.
In November 2013, Kaczynski reported that Kentucky Senator Rand Paul had plagiarized sections of a speech he gave in June 2013 on immigration from the Wikipedia article of the movie Stand and Deliver. Kaczynski subsequently reported Paul's 2012 book Government Bullies also contained passages that were plagiarized from articles from the right-wing think tank Heritage Foundation and from the libertarian Cato Institute. Further reports by Kaczynski revealed another four instances of plagiarism from an article by Case Western Reserve University professor Jonathan H. Adler and Pacific Legal Foundation attorney Timothy Sandefur. Another section of the book was discovered to be plagiarized from an article written in Forbes Magazine. The next year, Kaczynski continued with a series of articles chronicling politicians' plagiarism. Kaczynski found more than a dozen examples of politicians running for office in 2014 copying their plans and issues pages verbatim from other candidates. In January 2017, Kaczynski reported that Monica Crowley had plagiarized large sections of her 2012 book What The (Bleep) Just Happened. The publisher, HarperCollins, announced they would stop selling the book. The Trump Administration tapped Crowley to serve as senior director of strategic communications for the National Security Council. In May 2017, he reported that Sheriff David Clarke had plagiarized portions of his master's thesis.
Following the Boston Marathon bombings of 2013, he played a role in spreading unsubstantiated misinformation about the identities of the suspected bombers when he retweeted false reports made by Reddit user Greg Hughes.
In 2015, Politico reported Kaczynski was leading internal opposition research at BuzzFeed looking to dig up dirt on politicians. NPR reported Kaczynski's team dug up clips of Donald Trump saying he supported – despite statements to the contrary – the Iraq War; a clip of Hillary Clinton referring to some children as "super predators"; a video of Ben Carson saying he believed the pyramids were used to store grain; and a video of Bernie Sanders proclaiming his support for Fidel Castro and the Sandinistas in Nicaragua. Kaczynski subsequently found clips of Donald Trump supporting the 2011 American intervention in Libya, the toppling of Egyptian president Hosni Mubarak, and pushing for US action to protect Iranian protesters. Clips Kaczynski found of Donald Trump on the Howard Stern Show were used in both Democratic and Republican attack ads against Trump and as the basis of a question in the first general election Presidential debate of 2016. During the US campaign for president in 2016, Kaczynski brought to attention a statement by the chairman of the American Nazi Party in support of Republican candidate Donald Trump on the grounds that "if Trump does win ... it's going to be a real opportunity for people like white nationalists."
In January 2017, Kaczynski surfaced audio of Donald Trump's nominee for secretary of labor, Andrew Puzder, describing the employees hired at his restaurants as the "best of the worst". Puzder later withdrew due to other reasons, and did not join the administration.
On July 4, 2017, Kaczynski controversially reported he used "identifying information" to find the identity of a Reddit user who created a anti-CNN video meme President Donald Trump tweeted two days prior, using a Facebook search to find them. The Reddit account which had created the video meme had a history of posting racist, anti-semitic and homophobic comments and statements. Kaczynski reported the creator's identity would be withheld by CNN since the creator was a private citizen and because he had issued an "extensive apology." CNN editors then added the disclaimer "CNN reserves the right to publish his identity should any of that change." The disclaimer was subject to criticism that it created the appearance of blackmail, while conversely the article was also criticized for not revealing the subject's name. Kaczynski stated that the line was "misinterpreted" and that the user said that he was not threatened prior to his apology. Later it was reported that the video had been edited by at least one other person between the time it was posted on Reddit and when it was tweeted by Trump.
Time named Kaczynski's Twitter feed one of "The 140 Best Twitter Feeds of 2013", one of ten in the Politics category.
In 2013 he was listed on the Daily Beast website's "Beast Best" awards for his Twitter Feed.
In 2014, New York Magazine named him the 13th most influential Tweeter in New York City.
Slate political reporter Dave Weigel called him "the Oppenheimer of archival video research."
Politico named him one of the breakout stars of the 2016 election.
In 2017, he was nominated for the Shorty Award for Best Journalist.
He was described as a moderate Republican in a New York Magazine profile. It was later revealed Kaczynski was misquoted and called himself "a political moderate."
Kaczynski married Rachel Louise Ensign, a reporter for The Wall Street Journal, in May 2017.